<p> CHAPTER 9 NOTES The Cell Cycle . Remember: When cells get too large they cannot get enough nutrients into and out of the cell. . Cell division prevents the cell from becoming too large. . Cell division is the way the cell reproduces so that you grow and heal certain injuries. . Cell division is asexual reproduction meaning the offspring are clones/identical to the parent. . Cells reproduce by a cycle of growing and dividing called the cell cycle. . The cell cycle includes the following 5 phases . Interphase 4.1.G1 (1st growth phase) 4.2.S (Synthesis phase) 4.3.G2 (2nd growth phase) 4. Mitosis 5. Cytokinesis </p><p>. Interphase is the stage during which the cell grows, carries out cellular functions, and replicates. . Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. . Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell. The Stages of Interphase</p><p>. The first stage of interphase, G1 . The cell is growing, carrying out normal cell functions, and preparing to replicate DNA. . The Second Stage of Interphase, S . The cell copies its DNA in preparation for cell division.</p><p>. The Third Stage of Interphase, G2</p><p>. The cell prepares for the division of its nucleus. Mitosis . Mitosis is the division of the nucleus where the DNA is divided equally into two new nuclei. . During the S Phase of interphase, the DNA is copied . It is very important that all the DNA gets copied correctly and equally divided among the new nuclei so that the 2 new cells are exactly the same. . Incorrectly divided/copied DNA results in a mutation and possible cell death The Stages of Mitosis . There are 4 phases of Mitosis . Prophase . Metaphase . Anaphase . Telophase Prophase . The cell’s chromatin tightens. . Sister chromatids are attached at the centromere. . Spindle fibers form in the cytoplasm. . The nuclear envelope seems to disappear. . Spindle fibers attach to the sister chromatids Metaphase . Sister chromatids are pulled along the spindle apparatus toward the center of the cell. . They line up in the middle of the cell. Anaphase . The microtubules of the spindle apparatus begin to shorten. . The sister chromatids separate. . The chromosomes move toward the poles of the cell. Telophase . Two new nuclear membranes begin to form around the DNA and the nucleoli reappear. . The spindle apparatus disassembles. Cytokinesis . Cytokinesis is the final step of the cell cycle where the cell’s cytoplasm divides into 2 new cells . In animal cells, microfilaments constrict, or pinch, the cytoplasm. . In plant cells, a new structure, called a cell plate, forms. Normal Cell Cycle . The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong. . If the cell cycle is not monitored, then cancer can result.</p><p>Abnormal Cell Cycle: Cancer . Cancer is the uncontrolled growth and division of cells. . Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function. Causes of Cancer . The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations. . Various environmental factors can affect the occurrence of cancer cells. . Cigarette smoke – lung cancer . Asbestos – lung cancer . Sun Exposure – skin cancer and cataracts</p>